The have previously been proposed stent delivery systems for putting a stent in a stenosed part or occluded part formed in a living body lumen or body cavity such as a blood vessel, bile duct, esophagus, trachea, urethra, digestive tract and other organs, so as to secure or keep open the lumen or body cavity space.
Stents used with the above-mentioned stent delivery systems are classified into balloon-expandable type stents and self-expandable type stents, according to the function of the stent and the method of indwelling the stent.
The balloon-expandable type stent is a stent which itself does not have an expanding function. In order to put this type of stent in a target part, for example, the stent mounted on a balloon is inserted into the target part, and thereafter the stent is expanded (plastically deformed) by dilating the balloon, whereby the stent is put into firm contact with the inner surface of the target part and fixed there.
Though this type of stent needs the stent-expanding operation as above-mentioned, the stent can be indwelled by mounting the stent directly onto the contracted balloon, so that there is little problem with respect to indwelling the stent.
On the other hand, the self-expandable type stent is a stent which itself has contracting and expanding functions. In order to put this type of stent indwelling in a target part, the stent in contracted state is inserted into the target part, and then the stress loaded on the stent for maintaining the contracted state is removed. For example, the stent is contained in a contracted state in a sheath having an outside diameter smaller than the inside diameter of the target part, the distal end of the sheath is caused to reach the target part, and thereafter the stent is pushed out of the sheath. The stent thus pushed out is released from the sheath, whereby the stress load is removed, so that the stent is allowed to expand to be restored to its pre-contraction shape. This results in the stent being put into firm contact with the inner surface of the target part and fixed there.
Since this type of stent itself has an expanding force, the need for an expanding operation as in the case of a balloon-expandable type stent is absent, so that the stent is free of the problem that its diameter might be gradually decreased by the blood vessel's pressure or the like with the result of restenosis.
However, a self-expandable type stent is generally said to be more difficult than a balloon-expandable type stent to indwell in an accurate manner. The reason is as follows. In the case of a balloon-expandable type stent, after the stent is disposed in a target stenosed part, it is only necessary to inject a fluid into the balloon, so that the stent is typically not moved forward or backward at the time of expansion. On the other hand, the delivery system for a self-expandable type stent is so structured that the stent is contained and restrained between an inner tube and an outer tube, the inner tube is provided on the stent proximal side with an lock section for restricting movement of the stent, and the restraint on the stent is released by pulling the outer tube toward the proximal side, thereby allowing the stent to self-expand. In this case, the stent is liable to move forward at the time of expansion, due to sagging of the outer tube in the body cavity, friction between the outer tube and the body cavity or the catheter in which the outer tube is introduced, or friction between the outer tube and a valve of a device, called introducer, for introducing the system into the living body.
In view of the foregoing, the present applicant has proposed stent delivery systems as shown in Japanese Patent Application Publication No. 2008-272261 (U.S. Patent Application Publication No. 2010/0076541 and European Patent Application Publication No. 2143404) and Japanese Patent Application Publication No. 2008-272262 (U.S. Patent Application Publication No. 2010/0076541, European Patent Application Publication No. 2143404).
The stent delivery system 1 according to Japanese Patent Application Publication No. 2008-272261 includes a distal-side tube 2, a proximal-side tube 4, a slide tube 7 disposed so as to be proximate to the proximal end of a stent containing tubular member 5, a fixing tube 8 to which the distal-side tube 2 and the proximal-side tube 4 are fixed and which can contain the slide tube 7, and pulling wires 6a, 6b for moving the tubular member 5 toward the proximal side.
In addition, the stent delivery system 1 according to the Japanese Patent Application Publication No. 2008-272262 includes a distal-side tube 2, a proximal-side tube 4, a slide tube 7 which is proximate to the proximal end of the stent containing tubular member 5 and which is not fixed to the tubular member 5, a fixing tube 8 to which the distal-side tube 2 and the proximal-side tube 4 are fixed and which can contain the slide tube 7, and a pulling wire 6 for moving the tubular member 5 toward the proximal side. The slide tube 7 can be moved toward the proximal side by pulling of the pulling wire 6, and has a ring-shaped member 75 which is contained therein, to which the pulling wire is fixed, and which can be moved together with the slide tube.
In addition, in this stent delivery system, an opening section for leading out a guide wire inserted via a distal opening of the distal-side tube is provided not at the proximal end of the delivery system but in the fixing tube, so that the operation of exchanging the stent delivery system with another stent delivery system in the process of putting the stent indwelling is easy to carry out. Because the stent can be released by pulling the pulling wire toward the proximal side, positional shifting of the stent at the time of the stent-releasing operation is extremely little. Further, this stent delivery system is advantageous in that unnecessary bending of or damage to a catheter is not generated due to excessive winding-up of the wire for pulling the stent containing tubular member toward the proximal side.
A stent delivery system is inserted into a living body after a priming process for replacement of air in the inside of the system with liquid is carried out. In the stent delivery systems according to the two Japanese application publications mentioned above, the priming process for the spaces formed between the distal-side tube 2 and each of the stent containing tubular member 5, the slide tube 7 and the fixing tube 8 has not necessarily been easy to carry out.